Is it advisable to add an appendix section in a review paper? [closed]

Question

Background: There is an untapped aspect of a domain which I am currently writing a review paper in. The review paper is encompassing the domain in general.

I want to add a short one page proposal of that "untapped aspect" so as to carry forward future research. I plan to add this in the review.

Options

1. Should I just leave it out of the review and draft that as a separate paper with personal experimentation?
2. Should I add it as a appendix in our paper? (no experimentation).

Should I go for option 1 or 2?

Note: There is no page limit and appendixes are allowed in the journal.

Answer 1

If the paper has been refereed and the referee has not suggested adding an appendix, you should not do Option 2 (or at least you need to get a permission from the handling editor/referee). If the paper has not been refereed yet, you can do whatever you and your co-authors want. Option 1 (publishing a 1-page separate paper) is bad.

Answer 2

A review paper summarises the current state of knowledge. Stating opening problems (untapped aspects) adds value and can be included. I see no reason to include such problems in an appendix; they could appear in the main body. It's a personal preference as to whether they appear in your review paper or a separate paper which states the problem and provides a solution. At least, it is without further details. E.g., if the open problem is unknown, worthy of extended discussion, and/or identification has value, then unveiling in a separate paper focusing on the problem/solution may have benefits.

Answer 3

If you are not afraid of losing your head position, you can add that part - perhaps briefly - to the review. In my field it is normal that a review can ends with a Perspectives section.

Depending on details that you are the only one aware of, you can even do so and proceed immediately to the dedicated possible paper you have mentioned.